The present invention relates to smoking articles, such as cigarettes, and in particular to filter cigarettes.
Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge or roll of smokable material, such as shredded tobacco (e.g., tobacco cut filler), surrounded by a paper wrapper, thereby forming a so-called "tobacco rod." It has become desirable to manufacture a cigarette having a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element is manufactured from cellulose acetate tow and plug wrap, and is attached to the tobacco rod using a circumscribing tipping material. Cigarettes having filter elements are referred to as "filter cigarettes."
A ventilated or air diluted cigarette normally includes a filter element having a zone of a predetermined permeability so that air can dilute drawn mainstream smoke which passes to the mouth of the smoker. One convenient method for providing air diluted filter cigarettes involves a so-called "on-line" laser perforation technique, whereby a row of vents is provided around the cigarette through the tipping material and plug wrap of the filter element.
Normally, gas phase components of tobacco smoke (e.g., carbon monoxide and nitrogen oxides) are reduced within the mainstream smoke of ventilated cigarettes. Furthermore, the FTC "tar" yields of ventilated cigarettes are reduced. However, filter elements also are relatively efficient for the removal of particulate matter from mainstream tobacco smoke, and as such, there is not provided a reduction in the ratio of the gas phase components of the mainstream smoke relative to the FTC "tar" yields of ventilated cigarettes.
Filter elements having low efficiencies for the removal of particulate matter from mainstream tobacco smoke have been proposed. However, a low efficiency filter element, in conjunction with the ventilation provided to the cigarette, provides a cigarette having a relatively low resistance to draw. Many smokers find cigarettes having low draw resistances frustrating and unacceptable. See, Tobacco Encyclopedia, edited by Voges, TJI (1984).
It would be desirable to provide a filter element for a cigarette, which filter element exhibits both a relatively low filtration efficiency for particulate matter of mainstream cigarette smoke and a relatively high resistance to draw.